1. Field of the Invention
The present invention relates generally to the field of measurement and automation systems. More particularly, the present invention relates to a node in a graphical program which is useable to generate an executable program for performing a measurement task.
2. Description of the Related Art
Scientists and engineers often use measurement or automation systems to perform a variety of functions, including measurement of a physical phenomenon or unit under test (UUT), test and analysis of physical phenomena, simulation, hardware-in-the-loop testing, process monitoring and control, control of mechanical or electrical machinery, data logging, laboratory research, and analytical chemistry, to name a few examples.
A typical measurement system includes a computer system with a measurement device or measurement hardware. The measurement device may be or include a computer-based instrument, a data acquisition device or board, a programmable logic device (PLD), a sensor, a smart sensor, an actuator, a signal generator, or other type of device for acquiring or generating data. The measurement device may be a card or board plugged into one of the I/O slots of the computer system, a card or board plugged into a chassis, or an external device. For example, in a common measurement system configuration, the measurement hardware is coupled to the computer system via other means such as through a VXI (VME eXtensions for Instrumentation) bus, a PXI (PCI eXtensions for Instrumentation) bus, a GPIB (General Purpose Interface Bus), a serial port, or a parallel port of the computer system. Optionally, the measurement system includes signal conditioning devices which receive the field signals and condition the signals to be acquired.
A measurement system may also typically include transducers, sensors, actuators or other detecting (or generating) means for providing “field” electrical signals representing a process, physical phenomena, equipment being monitored or measured, etc. The field signals are provided to the measurement hardware.
The measurement hardware is configured and controlled by measurement software executing on the computer system. The measurement software for configuring and controlling the measurement system typically comprises two portions: the device interface or driver-level software and the application software, or the application. The driver-level software serves to interface the measurement hardware to the application. The driver-level software may be supplied by the manufacturer of the measurement hardware or by some other third party software vendor. An example of measurement or DAQ driver-level software is NI-DAQ from National Instruments Corporation. The application or client is typically developed by the user of the measurement system and is tailored to the particular function which the user intends the measurement system to perform. The measurement hardware manufacturer or third party software vendor sometimes supplies the application software for certain applications which are common, generic or straightforward.
One drawback of some current measurement system architectures is that complex measurement tasks involving multiple devices require that each device be programmed separately, and that synchronization signals be explicitly routed. Users must typically specify and configure measurement tasks at an advanced level, which is time consuming, expensive, and prone to error. For example, in some prior art systems, users must specify numerous parameter values for channels, timing, and triggering for a measurement task. Typically there is no mechanism for providing default values for the parameters, so that the user must not only know all of the parameters which are needed to specify the task, but must also know what values of the parameters are appropriate for the task. These issues may become more important when multiple devices are utilized to perform the task, in that the number and variety of parameters may increase accordingly.
Additionally, many current measurement systems require that the user perform a significant amount of programming, either in a text-based programming language such as LabWindows or Visual Basic, or in a graphical programming language such as LabVIEW. It would be desirable for a user to be able to more easily create measurement solutions with reduced programming requirements.
Therefore, it would be desirable to provide new systems and methods for specifying and performing measurement tasks.